Modular synthesis of diphosphoramidite ligands derived from 1,8,10,9-triazaboradecalin and their complexes with Ni, Pd, and Pt

Leveraging Metal and Ligand Reactive Sites for One Pot Reactions: Ligand‐Centered Borenium Ions for Tandem Catalysis with Palladium

“…Diels–Alder (DA) reactivity with R TBDPhos complexes was first established by screening the reactivity of the 2‐bromo‐1,3‐butadiene 1 , acrolein ( 2 a ), and 10 mol% ( MeO TBDPhos)PdCl 2 [12] with different solvents and Brønsted acid activators (Table 1). Although several TBDPhos derivatives are known, ( MeO TBDPhos)PdCl 2 was initially selected because we had shown previously that the methoxy substituents attached to phosphorus give rise to higher reactivity at the TBD backbone when compared to other substituents (as discussed below) [8d] .…”

“…With optimized conditions in hand, we tested several other variations of ( R TBDPhos)PdCl 2 with different R substituents attached to phosphorus (Figure 2). [12] Prior DFT studies of ligand‐centered reactions with ( R TBDPhos)Pt(S 2 C 6 H 4 ) and MeOH showed that that the reactions were ca. 5 kcal/mol more exergonic with R=MeO compared to R=Ph [8d] .…”

“…To further corroborate that the DA reactions occur at boron and not Pd, we performed an additional control reaction with the 1,2‐benzenedithiolate complex ( MeO TBDPhos)Pd(S 2 C 6 H 4 ). [12] We have shown in previous studies how the chloride ligands in related ( Ph TBDPhos)NiCl 2 are labile in the presence of acids like HNTf 2 , [8a] so we had to consider the possibility that chloride displacement from the metal could provide open coordination sites where potential DA reactions could occur. Even though this chloride displacement is also likely to occur in the control reaction with (dppe)PdCl 2 and HNTf 2 (which showed no DA reactivity), we tested the 16‐electron ( MeO TBDPhos)Pd(S 2 C 6 H 4 ) with chelating and more strongly bound dithiolate to further rule out the possibility of metal involvement.…”

Fluorination and hydrolytic stability of water-soluble platinum complexes with a borane-bridged diphosphoramidite ligand

“…However, we discovered that the same fluorination method with KF and Kryptofix 222 could be used with the closely related complex ( iPrO TBDPhos)PtCl 2 ( 3 ). 23 This complex is not appreciably soluble in water due to the more lipophilic isopropyl groups ( i.e. not useful for aqueous applications), but it yielded X-ray quality crystals of ( iPrO TBDPhos-HF)PtCl 2 ( 3-HF ) to structurally confirm successful addition of fluoride (Fig.…”

“…The remaining bond distances and angles for 3-HF are similar to those reported previously for 3 . 23…”